A 36 year-old female visited our clinic with a complaint of the upper abdominal pain. Next day we examined by ultrasonography and found that her gastric wall was thickened remarkably and diffusely, from the pylorus to the gastric body (about 12 mm). Its surface was smooth and the thickened wall echo was low. Gastrofiberscope showed an elevated lesion and a small worm was hanging in its center. This worm was removed by endoscope, and was found to be an anisakis. Her symptom was diminished, and one month later, ultrasonography showed the normal thin gastric wall. Ultrasonography is useful to find inflammatory diseases of the stomach by thickning of the wall.